Why Did Last Week's Solar Storm Take out SpaceX's Batch of Starlink Satellites?

By now, the story has gotten around that last Thursday's Starlink mission was struck by a geomagnetic or solar storm on Friday and 40 of the 49 satellites (at last update) were lost as result.  Most coverage focuses on what happened, which is fine.  To me, a better question is why did it happen.

Let me recap the what.  Yesterday's updates on the update sub-page to SpaceX's launches page has the best summary of what happened.  The essence goes like this;

Thursday's launch put the satellites into the desired orbit, with the perigee (lowest point) of approximately 210 kilometers above Earth (130 miles), and each satellite achieved controlled flight. This approach is risky for SpaceX; the satellites are there just long enough to be checked out, but they feel it's better for everyone sharing orbital space to do it this way.  Satellites that pass the checkout fire their onboard ion thrusters to raise their orbit to the desired altitude.  Any that fail their checkout are allowed to re-enter the atmosphere, burning up completely.  The unexpected part was that on Friday, the solar storm stuck. 

The storm heated the upper atmosphere, causing it to expand upward, which then caused the drag on the satellites to increase.  SpaceX reported that their onboard GPS suggested the storm caused atmospheric drag to increase up to 50 percent higher than during previous launches.  The Starlink team commanded the satellites into a safe-mode where they would fly edge-on (like a sheet of paper) to minimize drag—to effectively “take cover from the storm”—and continued to work closely with the Space Force’s 18th Space Control Squadron and LeoLabs to provide updates on the satellites based on ground radars. 

The thing is, this was not a strong solar storm.  There are several ways solar storms like this are monitored, two of the most common and widely available are called the A and K indices (pdf).  They're both measurements of geomagnetic activity, taken differently and so they have different scales.  A very common way to track activity is what's referred to as the Planetary K index, abbreviated Kp. I was able to find the relevant chart in a video that I have more to say about, but first the chart:

The storm that disabled the satellites is marked by the two red bars toward the right on February 4th.  The bars are three hours wide, which helps you visualize the storm's duration.  You'll note an almost identical storm the day before, roughly 0900 to 1200 UTC on the third, which was the night before and morning of the launch. 

The point to emphasize here is that Kp for the storm maxed out at five.  The scale is 0 to 9, but solar storms that raise Kp to five are roughly once a week to once every few weeks events.  During sunspot peaks, I recall days with the Kp at eight or nine for longer periods and in that red (> 4)  color for 24 hours or more.  Further, in the video that graph is from, the narrator says he knows SpaceX has launched into storms this strong before without this kind of trouble.  Which brings us back to the question of why.  

The video is from a YouTube channel that puts together some interesting stuff under the name Suspicious 0bservers (note the zero, not "O"), run by a guy named Ben Davidson.  He's frankly hard to describe, but I think the term he'd use is that he's a catastrophist; he sees evidence for periodic or cyclic catastrophes that appear in history over and over.  Sort of the geological/astronomical equivalent of the people who see history as Kondratiev Waves, Elliot Waves or First through Fourth Turnings. 

One of the topics he talks about often is the wandering magnetic poles we're seeing and our weakening magnetic field.  That's his explanation for why this mission was affected more than others.  I have a hard time with that because while it's well established that there has been a lot of pole movement in the last 20 years, and our magnetic field has weakened, why didn't other missions have the same problem?  If similar solar storms in the last couple of years didn't lead to loss of the satellites, what (if anything) does that say about how much weaker the field has become?   Is it half as strong? 90% as strong?  Down to 1/10 as strong? 

My disappointing conclusion is that I can't answer why.  There have been roughly three dozen launches of Starlink satellites and roughly 1,900 in orbit now.  Granted the last four years have been pretty low in solar activity, but if Davidson is right about them launching in similar solar storms on prior missions, something different happened this time.  Maybe it was some perfectly wrong flicker of the magnetic field or the solar storm that hasn't been documented.  Not knowing what caused it is bound to cause heartburn in the folks deciding if they'll launch under these conditions.